1. What's wrong with PDF? The format has been around for 30+ years now, and PDFs that old display just fine on any open-source PDF-viewing program now.

3. Redundant copies aren't going to last 100 years unless they're on some medium that can actually last that long, such as an aluminum (i.e., factory-made, not burned) CD. A flash thumb drive isn't going to last that long, not even close.